Heat exchange apparatus



June 2; 19310 E, s v 1,807,638

HEAT EXCHANGE APPARATUS Filed Nov. 9, 1928 2 Sheets-Sheet l June 2, 1931.

E. SEAVER 1,807,638

HEAT EXCHANGE APPARATUS Filed Nov. 9, 1928 2 Sheets-Sheet 2 Patented June 2, 1931 PATENT OFFICE EDWARD SEAVER, F NEEDHAM, MASSACHUSETTS HEAT EXCHANGE APPARATUS Application filed Ngvember 9, 1928.

The present invention relates to heat exchange apparatus and methods of assembling the same.

In heat exchange apparatus employing water tubes, each tube is subject at the entrance end to corrosive and erosive effects of the water. The corrosion at the entrance end of the tube follows from the fact that the incoming water does not completely fill the tube but enters in a constricted stream which permits a pocket of air or other gases to act upon the tube. The turbulence resulting from this constricted fiow gives rise to an erosive action. Since the tubes are necessarily made as thin as possible to afford high capacity for heat transfer, the wear on the entrance end of each tube is considerable, necessitating not only a heavy expense for replacement of the tubes themselves, but also because of the frequent shutdowns, a loss of use of the equipment. An added difficulty arises from the use of packed connections, which are sometimes employed, in that the necessary clearance between the tube and the ferrule sets up additional turbulence, and also provides a space for the deposit of silt or scale which increases the corrosive action.

The principal object of the present invention is to provide a water tube assembly and method of making the same whereby the detrimental action of the water on the tubes is substantially eliminated.

A further object of the invention is to provide a water tube assembly in which corrosive and erosive actions, if they occur, are ineffective to attack the relatively thin tube itself and are localized in a part which is able to withstand the wear and which may, if necessary, be readily replaced.

With these objects in View, the present invention consists in the heat exchange apparatus and methods of assembling the same hereinafter described and particularly defined in the claims. r

In the accompanying drawings, Fig. 1 is a horizontal section of a portion of the heat exchange apparatus, such as a condenser, embodying the features of the present invention;

Serial No. 318,253.

Fig. 2 is a horizontal sectional detail view showing the preferred form of the present invention Fig. 3 is a detail view showing a modified form of the invention;

Fig. 4 is a detail view showing another modified form of the invention;

Fig. 5 is a still further modification of a type of construction adapted for existing installations; and

Fig. 6 is a modification of the construction shown in Fig. 5.

The illustrated embodiment of the invention comprises a surface condenser comprising a bank of tubes through which the cooling water flows and about the exterior of which the steam is passed. Referring to Fig. 1, the apparatus comprises an entrance tube sheet 2, an exit tube sheet 4, and a bank of tubes 6 connected between the tube sheets. The tubes are received in the exit sheet 4 by means of ferrules 8 cooperating with a metallic packing 10. The construction at the exit end of the tubes is such as to provide for expansion upon changes in temperature. Since the detrimental effects of the water are not apparent to any appreciable extent at the exit end, the construction thus far described is not of primary importance, and any usual or preferred form of attaching means for the exit ends ofthe tubes may be employed.

The water is conducted to the tubes at their entrance ends through guiding or entrance nozzles 12. In the form of the invention, as shown in Fig. 2, each entrance nozzle 12 comprises a tubular body extending outwardly from the tube sheet to conduct water from the Water box into the tube. The. nozzle is of considerable thickness compared to the thickness of the tube. The tube sheet is formed with a threadcd'recess in which the exteriorly threaded end 14 of the nozzle is received. The tube 6 projects into a tube-receiving aperture formed in the tube sheet, as indicated at 16, this aperture forming a continuation of the larger nozzlereceiving recess. The end of the nozzle abuts the entrance end of the tube at the joint, indicated at 18, and the inner end of til) the nozzle is therefore preferably formed with an accurate shoulder in order to assure a smooth fit where the tube and nozzle abut. At its inner end, the nozzle is of a diameter as nearly equal as possible to the internal diameter of the tube, and at its entrance end the nozzle is rounded, as shown at 20, to form a substantial stream line entrance for the water. The nozzle is slotted at 22 to afford means for threading the nozzle into the tube sheet.

After assembly of the tubes and nozzles in the tube sheet, an expanding tool is run into each nozzle and is caused to expand the metal of the tube and nozzle over approximately the space indicated at 24. This expanding operation is carried out by an expander of any usual form. it acts to force the metal of the tube into engagement with the tube sheet, thus forming a tight joint to preventleakage of water into the steam space, and in addition to present a smooth and continuous inner bore to the water at the junction of the nozzle and tube. The tubes and nozzles are of metal brass or steel alloys, which have some ductility, and the expanding operation, therefore, causes a sufiicient flow of metal to force the tube and nozzle into close engagement with each other. Even though the tubes and nozzles are made with a slight tolerance or may be slightly out of round at the ends. the expanding action causes such a flow or metal as practical to smooth the joint between the tube and nozzle against any irregularities in surface. The expanding action also serves to force the metal of the nozzle into engagement with the tube sheet along the threads. Inasmuch as the nozzle is of relatively ductile material, this expanding operation effects a substantial bond which is mechanically strong and also resists leakage of water into the joint. The ductility of the nozzle, how ver, permits removal thereof from the tube sheet whenever necessary, the threads on the tube sheet being unharmed by the expanding operation.

It will be seen that the entrance nozzle is so designed at its en rance end that it substantially conforms to the path of water flow. The corrosive effect of an air pocket is therefore largely eliminated. Moreover, the turbulence of flow is considerably reduced and as a result, the or sive action is minimizer The nozzle is of such a length that corrosive and erosive actions, if they occur at all, are localized in the nozzle itself and do not reach into the tube. Since the nozzle is of relatively heavy material, the wear occasioned by the water is of rela tively small importance and when it does become of consequence, the nozzle can be readily replaced without removal of the tube. Upon replacement of a nozzle, the new nozzle is threaded into the tube sheet Lsovgcss until it firmly abuts the end of the tube and another expanding operation is performed to make a smooth tight joint between the nozzle and the tube. The joint 18 is in all cases smooth and continuous, and presents no irregularities to permit a deposit of silt or scale. The joint that may be obtained by an expanding operation is such as to make an apparently continuous length of water passage from the entrance end of the nozzle to the exit end of the tube.

In the construction shown in Fig. 3, the entrance tube sheet 2 is provided with a threaded nozzle-receiving recess as in the construction described above. The tube 26, however, is positioned in the tube sheet so that its end is substantially flush with the outer surface of the tube sheet. The nozzle 28 is in form similar to the nozzle 12 de scribed. above, having an exteriorly threaded end 30 to be received in the tube sheet. The interior of the nozzle has a threaded counterbore to receive the end of the tube 26. The end of the tube abuts a shoulder 34; of the nozzle, the tube and nozzle being of equal internal diameters to aliord a smooth uninterrupted joint. After assembly of the parts, an expanding tool is caused to operate over the length indicated approximately at 36. The expanding action is to force the tube into engagement with the tube sheet and with the internal threads of the nozzle, and to make a smooth, tight joint between the tube and nozzle. The nozzle itself is forced into engagement with the tube sheet as in the construction previously described.

in the construction shown in Fig. l, the entrance tube sheet is shown at and the tube :2 extends completely through the tube sheet. The entrance nozzle 4A is of the same general form as the nozzle previously described, but is not threaded. The inner end of the nozzle is counterbored to receive the entrance end of the tube, the shoulder 46 of the counterbore abutting tightly against the end of the tube. After assembly, the expanding tool operates over the length of tube and nozzle, indicated at 48, as well as on the length of tube engaging with the tube sheet. In this modification, as in '1 the other forms of the invention, a smooth, continuous and tight joint is provided at the shoulder 46. The construction is one which may be applied to existing plants with very little difiiculty because of the fact that no machining of the tube sheet is necessary.

The construction shown in Figs. 5 and (5 is particularly adapted to existing installations in which it desired to replace the usual ferrule surrounding the tube end. In the construction shown in Fig. 5, the tube end projects within the opening in the tube sheet, and is surrounded intermediate the opposite sides of the tube sheet by a packing 50, preferably of fibrous material. A

nozzle 52 is threaded at 54: within the recess already present in the tube sheet, the shouldered portions 56 of the nozzle abutting the outer surface of the tube sheet. Thereafter the tube 6 is expanded into engagement with the packing, the tube sheet, and the inner bore of the nozzle throughout the region 58 to seal against leakage and provide a smooth, continuous, inner bore, leaving no gap at the junction between the tube end and the inner shoulder 60 formed upon the nozzle. The construction shown in Fig. 6 is similar to that of Fig. 5, with the single exception that sufiicient thickness is allowed at the inner end of the nozzle for the provision of internal threads 62 into which the material of the tube end 6 is partially flowed during the process of expanding the tube end into the nozzle and surrounding tube sheet.

It will be evident from the foregoing description that all of the herein described constructions, whether applied to existing forms of water tube assemblies or developed as new assemblies, embodying the characteristic feature of an entrance nozzle having a substantially greater wall thickness than that of the conventional tube and of sufficient length to confine turbulence and eddy currents within the region of the nozzle, the junction between the nozzle and the abutting end of the tube being free from gaps, shoulders, or projections to form localized eddy currents, and presenting a smooth, continuous and unbroken inner bore for the flow of water from the entrance point of the nozzle to the tube intermediate its ends. With this construction, it will be evident that the erosive effects of water turbulence and eddy currents are practically removed from the tube structure. correspondingly, the tube structure may be made with a desirably thin wall to facilitate heat exchange, the corrosive effects upon the tube wall'being reduced and minimized, due to continuity of flow therethrough, and the confinement of localized actions, if any, to the region of the nozzle.

What is claimed is:

1. Heat exchange apparatus comprising an entrance tube sheet, water tubes secured in the tube sheet, an entrance nozzle for each tube to guide Water to the tube and extending outwardly beyond the tube sheet, the nozzle being of sufficient length to confine turbulence, the tube and nozzle being of the same internal diameter and abutting each other, the metal of the tube and nozzle being expanded to form a smooth and continuous inner bore.

2. Heat exchange apparatus comprising a tube sheet, water tubes secured in the tube sheet, an entrance nozzle for each tube, the tube and nozzle having abutting surfaces and being of the same internal diameter at their junction, the nozzle having relatively thick walls compared to the tube to resist corrosion, and the tube and nozzle forming a smooth and continuous inner bore to permit uninterrupted flow of water at their junction.

'3. Heat exchange apparatus comprising a tube sheet, water tubes secured in the tube sheet, an entrance nozzle for each tube extending outwardly beyond the tube sheet, the tube and nozzle abutting each other and being expanded together to form a smooth, continuous surface at their junction, the nozzle being of considerable thickness compared tothat of the tube and having a rounded inlet to guide the water interiorly of the nozzle.

4. Heat exchange apparatus comprising an entrance tube sheet and water tubes secured in the tube sheet, an entrance nozzle for each tube having threaded engagement withthe tube sheet and having a surface abutting the end of the tube, the nozzle extending outwardly beyond the tube sheetand being of sufiicient length to confine turbulence, the tube and nozzle being expanded to form a smooth and continuous surface at their junction.

5. Heat exchange apparatus comprising an entrance tubesheet having apertures to receive tubes and a threaded nozzle-receiving recess associated with each tube aperture, water tubes secured in the apertures, a nozzle having a threaded end received in the nozzle-receiving recess and abutting the entrance end of each tube, the abutting surfaces of the tubes and nozzles forming smooth and uninterrupted junctions of uniform diameter to permit uniform flow of water.

6. Heat exchange apparatus comprising an. entrance tube sheet having a plurality of tube apertures and a plurality of nozzle-receiving recesses extending partially through the tube sheet, water tubes secured in the tube apertures and extending slightly into the nozzle recess, a nozzle for each tube threaded in the tube sheet and having a shoulder abutting the end of the tube to form a smooth, continuous junction of uniform diameter.

7. A method of assembling heat exchange apparatus which consists in positioning a water tube in a tube sheet with its end between the opposite sides of the tube sheet, threading an entrance nozzle in the tube sheet with its end abutting the entrance end of the tube, and expanding the metal of the tube'and nozzle to form a smooth and continuous surface at the junction of the tube and nozzle.

' 8. Heat exchange apparatus comprising an entrance tube sheet, a series of water tubes mounted in the sheet, an entrance nozzle for each tube to guide water to the tube extending outwardly beyond the sheet, the tube and nozzle having the same internal diameter, and the nozzle provided with a recessed portion in which the end of the tube is expanded to form a smooth and continuous inner bore at the junction.

9. Heat exchange apparatus comprising a series of relatively thin wall tubes adapted to convey water therethrough and facilitate heat interchange, an entrance nozzle connected With the entrance end of each tube and having a Wall thickness substantially greater than that of the tube, the entrance nozzle being of suflicient length to confine turbulence, due to entering Water flow Within the region of the nozzle, and presenting, in combination with. the tube, a smooth and substantially continuous inner bore for the flow of Water therethrough.

10. Heat exchange apparatus comprising an entrance tube sheet, a series of Water tubes mounted Within the sheet, a series of entrance nozzles detachably connected directly to the sheet and extending outwardly therebeyond to provide conduits of substantial length for directing Water to the tubes, the interior of each nozzle and connected tube being of the same diameter, and presenting a smooth and substantially contin uous inner bore for the flow of Water therethrough.

EDWARD SEAVER. 

